Modeling of light scattering and haze in semicrystalline polymers

This article reports a new model approach for the description of light scattering in semicrystalline polymers, to describe more precisely the influence of supermolecular structure on the optical properties. This is the first study in which light scattering of polymer films has been modeled using exact Mie scattering theory of radially anisotropic spheres. As a model material a well‐known polymer, isotactic polypropylene (iPP) was used. Samples were prepared with different sample thicknesses and crystalline structures in order to identify the key parameters of light scattering in polycrystalline polymeric systems. Validation haze measurements were carried out with a spectrophotometer equipped with a 150 mm snap‐in integrating sphere. It was found that the optical properties of the polycrystalline sample can be described using multiple light scattering on these scattering centers. Good agreement was found between the simulated and experimentally measured haze values which proves the reliability and applicability of our new approach. This work reports a new light scattering model of polymer films consisting of radially anisotropic spherulites using Mie scattering combined with multiple scattering theory. The model handles light scattering and haze as a function of sample thickness, spherulite size, birefringence, and wavelength accurately. By fitting the model to haze measurements, birefringence between 0.0015 and 0.0020 was obtained in the visible wavelength range.